I installed and run without problem (on my old XP laptop) its version 2.3.1 (likely its last one).
After hours (exploring the menus and documents), I couldn't find the way to how to set the MCU crystal frequency.

Naturally, in this case, the debugger (via internal simulator for C51ASM or SDCC project) cannot provide the processor timing (total or relative) in cycles and/or micro-seconds.